Multicast optical switch is a wavelength-independent optical device. It can divide one input optical signal into multiple output optical signals, and transmits them to different ports. As one of key devices of the next generation of ROADM (reconfigurable optical add-drop multiplexer) system, the multicast optical switch cooperate is used with wavelength-selection optical switch. It is possible to meet function requirements of the ROADM system of colorlessness, non-directionality and non-competitiveness, that is significant to increase flexibility and reduce cost of the network construction.
Currently, there are three implementation methods of multicast optical switch, i.e., splicing method, integrated method and free space method. For multicast optical switch in manner of splicing using planar lightwave circuit (PLC) splitter and light switch, ports between the splitter and the light switch need to be connected with optical path by using a lot of optical fibers, and with increase of the ports, assembly difficulty and volume will increase; For multicast optical switch in manner of integration using PLC integrated splitter and switch, technical difficulty thereof is high, and requirement on equipment is high, and control principle of the PLC switch itself will cause larger power consumption US Patent application US2013/0202297 related to two kinds of free space solutions, one of which is to use the PLC splitter plus reflector or reflector array to create multicast optical switch in manner of free space. It needs to use a lot of lens for transformation of spots of the PLC splitter, with high debugging difficulty and high cost; the other solution is to use mirror array which consists of reflectors with different reflectivities to realize function of the splitter. Because reflectivity of each reflector is different, assembly complexity and cost thereof is higher than those of the first solution. And there is a problem of interference existing in optical path disclosed in the patent application, in when there are multiple inputting ports, the inputting ports may be interfered by reflected light.